In prior art X-ray systems, the power supplies used for applying high voltages to X-ray tubes have generally included relatively large step-up transformers and capacitors with oil or other special insulating mediums and have been quite bulky and heavy in weight. When a movable or portable X-ray tube unit is desired, flexible high voltage cables have been used between the power supply and the tube unit, the cables also requiring oil or other special insulating mediums for proper insulation with respect to the very high voltages used. Arrangements have been provided in which high voltage power supply components have been located in the X-ray tube unit itself to eliminate the need for a high voltage cable. In such arrangements, the required size of the power supply components is reduced by using a higher operating frequency, such as 600 Hz rather than 60 Hz. Also, circuit arrangements have been used in which a pair of capacitors are charged from the secondary windings of a pair of transformers with the voltages across the capacitors and the voltages across the secondary windings being combined in series to produce an output voltage having a very high peak value, nearly equal to four times the peak value of the voltage across each transformer winding.
The voltage so produced is, however, of a pulsating form with the peak value being produced at only one point in each cycle of operation.
Accordingly, for portable or movable X-ray tube units, the choice has been between one in which the tube unit is connected to a heavy power supply through a high voltage cable or one in which the unit has a self-contained power supply but in which a pulsating voltage is applied to the X-ray tube.